No one remembers the ones they catch in time. Walid Saadaoui and Amar Hussein will quickly be forgotten and so will the carnage they planned to visit upon British Jews. The men were convicted at Preston Crown Court on Tuesday of preparing terrorist acts. A third man, Bilel Saadaoui, brother of Walid, was found guilty of failing to disclose information about planned terrorist acts. Walid plotted to open fire on a march against anti-Semitism in Manchester city centre before moving onto a Jewish area in the north of the city to continue the massacre. Police officers who got in the way were to be shot dead.

It is not enough to identify and prosecute individuals, the state has to root out cultures which have only been present in this country for a few generations but have already confirmed themselves as fundamental threats

Walid was no keyboard fantasist. In February 2024 he paid a deposit to smuggle two AK-47 rifles, two handguns and 900 rounds of ammunition into Britain. He reconned target sites across Greater Manchester, acquired a safe house, and recruited fellow Islamic State enthusiast Amar as his wingman. Walid confided his plans to his brother Bilel, also an Islamic State admirer, but while Bilel didn’t want to be part of the terror attack, he agreed to look after his brother’s financial arrangements, which included secreting £70,000 in a safe to prevent its seizure after the massacre. (British jihadist plots to commit mass murder but not before estate-planning to shield his assets from the state. Can’t get much more integrated than that.)

How many more Walid Saadaouis and Amar Husseins are out there in Britain, and how many Bilel Saadaouis? It’s the Bilels that should worry us the most. Islamism is the primary terrorist threat to the UK and while it is possible to detect, monitor and disrupt some – though not all or even most – plotters, the state is essentially powerless against those who sympathise with the jihadists, keep their secrets, turn a blind eye to red-flags, and do the small favours that smooth the path for larger outrages. Most Britons, upon learning that their brother was planning the mass murder of Jews, would go to the police. Bilel Saadaoui did not.

Whether that was out of ideological sympathy or familial loyalty, his actions were alien to British culture. They echo those cultures at work in Rotherham, Rochdale and elsewhere, in which the organised sexual exploitation of white British girls by mainly Pakistani-heritage men was able to take place in a semi-open fashion, in ways that created a significant number of witnesses, and yet prompted very few whistleblowers. While almost anyone from anywhere can be integrated and become a productive, valued member of UK society, there are cultures which are plainly incompatible with British norms.

It is not enough to identify and prosecute individuals, the state has to root out those cultures which have only been present in this country for a few generations but have already confirmed themselves as fundamental threats. As always, it’s important to underscore that we are talking about cultures — ideas, norms and practices — not ethnic or religious categories. Being a devout Muslim, or a thoroughly heretical one for that matter, is no barrier to Britishness. Being a Muslim prepared to kill for Islam, minded to impose Islamic preferences, or wishing to forcibly convert others — or one who greets these prospects with anything other than revulsion and rejection — is an insurmountable barrier to Britishness. We need to root out not only the Walids but the Bilels, too.

To do that, we must begin by accepting that multiculturalism is not only a false and failed doctrine but one that imperils national security and social cohesion. Individuals should be free to express their identity, celebrate their heritage, and practise their customs insofar as none of these threaten the existence of the state, contravene its laws, demand unreasonable accommodation, or attempt to supplant the dominant culture. For its part, the state should tackle the domestic Islamism problem via aggressive integration and a hostile environment – and tackle the Islamism importation problem via more stringent immigration and asylum policies.

I sketched out what these might look like in the wake of the Heaton Park synagogue shooting, but they should include providing services only in English (and other historic UK languages); proscribing cousin marriage; protecting the freedom to blaspheme, including by burning the Qur’an and depicting Mohammed; denying recourse to public funds to non-citizens; heavily taxing remittances; deporting migrants convicted of violent crimes or deemed to espouse Islamist views or behaviours; turning back Channel boats, detaining irregular migrants offshore, and deporting anyone who passes through a safe country to enter the UK.

These are crude measures, but crude measures are all we have left. As an astute friend says on this issue: ‘I wouldn’t have started from here,’ but here is where we are because successive governments threw open the doors to the country, welcomed in sizeable numbers from every conceivable culture, and asked little in terms of integration beyond the mouthing of some bromides about ‘British values’. The result has been plenty of patriotic, industrious, right-minded, good-hearted new Britons and some who are little more than ticking time bombs. We defused these ones in time. We aren’t always so lucky.

As a former idealist of both multiculturalism and mass immigration – and here ‘idealist’ should be understood to mean ‘damned bloody fool’ – I can only offer mea culpas and try to dissuade others from my foolishness by way of penance. Neither Walid nor Bilel Saadaoui is British, and nor is Amar Hussein. Their loyalty is to Islamism. That is their state, their flag and their culture. They are not our compatriots, they are the enemy within. The government should resolve to drive out this enemy and prevent it from entering in the first place.